warning report errors of various
dieis for fatal application errors. It prints a message to the user and exits with status 128.
usageis for errors in command line usage. After printing its message, it exits with status 129. (See also
usage_with_optionsin the parse-options API.)
erroris for non-fatal library errors. It prints a message to the user and returns -1 for convenience in signaling the error to the caller.
warningis for reporting situations that probably should not occur but which the user (and Git) can continue to work around without running into too many problems. Like
error, it returns -1 after reporting the situation to the caller.
Customizable error handlers
The default behavior of
error is to write a message to
stderr and then exit or return as appropriate. This behavior can be
example, "git daemon" uses set_die_routine to write the reason
was called to syslog before exiting.
Functions return a negative integer on error. Details beyond that vary from function to function:
Some functions return -1 for all errors. Others return a more specific value depending on how the caller might want to react to the error.
Some functions report the error to stderr with
error, while others leave that for the caller to do.
errno is not meaningful on return from most functions (except for thin wrappers for system calls).
Check the function’s API documentation to be sure.
An increasing number of functions take a parameter struct strbuf *err.
On error, such functions append a message about what went wrong to the
err strbuf. The message is meant to be complete enough to be passed
error as-is. For example:
if (ref_transaction_commit(transaction, &err)) die("%s", err.buf);
The err parameter will be untouched if no error occurred, so multiple function calls can be chained:
t = ref_transaction_begin(&err); if (!t || ref_transaction_update(t, "HEAD", ..., &err) || ret_transaction_commit(t, &err)) die("%s", err.buf);
The err parameter must be a pointer to a valid strbuf. To silence a message, pass a strbuf that is explicitly ignored:
if (thing_that_can_fail_in_an_ignorable_way(..., &err)) /* This failure is okay. */ strbuf_reset(&err);